Power supply apparatus converting input voltage to predetermined output voltage and controlling output voltage based on feedback signal corresponding to output voltage

1. A power supply apparatus having an input terminal and an output terminal, the power supply apparatus converting an input voltage at the input terminal into a predetermined output voltage at the output terminal, the power supply apparatus comprising:

a first power supply circuit that is coupled between the input terminal and the output terminal and converts the input voltage into a predetermined voltage to output the predetermined voltage;

a smoothing capacitor that is coupled to the output terminal; and

a second power supply circuit that outputs a predetermined voltage or current to the output terminal via the smoothing capacitor, based on a feedback signal corresponding to the predetermined output voltage.

2. The power supply apparatus as claimed in claim 1 ,

wherein the second power supply circuit converts a first direct-current voltage into a second direct-current voltage to output the second direct-current voltage to the smoothing capacitor, or the second power supply circuit converts a second direct-current voltage from the smoothing capacitor into a first direct-current voltage to output the first direct-current voltage.

3. The power supply apparatus as claimed in claim 1 ,

wherein the second power supply circuit converts a first direct-current voltage into a second direct-current voltage to output the second direct-current voltage to the smoothing capacitor.

4. The power supply apparatus as claimed in claim 1 ,

wherein the second power supply circuit includes a step-up and step-down converter.

5. The power supply apparatus as claimed in claim 2 ,

wherein the second power supply circuit includes a step-up and step-down converter.

6. The power supply apparatus as claimed in claim 1 ,

wherein the second power supply circuit includes a linear regulator.

7. The power supply apparatus as claimed in claim 3 ,

wherein the second power supply circuit includes a linear regulator.

8. The power supply apparatus as claimed in claim 1 ,

wherein the first power supply circuit includes a DCDC converter.

9. The power supply apparatus as claimed in claim 2 ,

wherein the first power supply circuit includes a DCDC converter.

10. The power supply apparatus as claimed in claim 1 ,

wherein the first power supply circuit includes a power factor correction circuit.

11. The power supply apparatus as claimed in claim 2 ,

wherein the first power supply circuit includes a power factor correction circuit.

12. The power supply apparatus as claimed in claim 8 ,

wherein the DCDC converter includes a step-up and step-down converter.

13. The power supply apparatus as claimed in claim 10 ,

wherein the power factor correction circuit includes a step-up and step-down converter.

14. The power supply apparatus as claimed in claim 1 , further comprising:

a voltage dividing circuit that includes a first resistor and a second resistor, performs voltage division on a voltage at the output terminal, and generates a feedback signal having a voltage obtained by the voltage division; and

a control signal generator circuit that generates a control signal for making a current flowing through the first resistor constant, to output the control signal to the second power supply circuit, based on the feedback signal.

15. The power supply apparatus as claimed in claim 14 ,

wherein the control signal generator circuit includes a differential amplifier that outputs, as the control signal, a voltage difference between the voltage of the feedback signal and a predetermined threshold voltage.

16. The power supply apparatus as claimed in claim 14 ,

wherein the first resistor is a load of the power supply apparatus.

17. Electronic equipment comprising:

a power supply apparatus that has an input terminal and an output terminal and converts an input voltage at the input terminal into a predetermined output voltage at the output terminal to output the predetermined output voltage to an electronic circuit,

wherein the power supply apparatus includes:

a first power supply circuit that is coupled between the input terminal and the output terminal and converts the input voltage into a predetermined voltage to output the predetermined voltage;

a smoothing capacitor that is coupled to the output terminal; and

a second power supply circuit that outputs a predetermined voltage or current to the output terminal via the smoothing capacitor, based on a feedback signal corresponding to the predetermined output voltage.

18. The electronic equipment as claimed in claim 17 ,

wherein the second power supply circuit converts a first direct-current voltage into a second direct-current voltage to output the second direct-current voltage to the smoothing capacitor, or the second power supply circuit converts a second direct-current voltage from the smoothing capacitor into a first direct-current voltage to output the first direct-current voltage.

19. A power supply circuit for a power supply apparatus that has an input terminal and an output terminal and converts an input voltage at the input terminal into a predetermined output voltage at the output terminal to output the predetermined output voltage to a load,

wherein the power supply apparatus includes:

a first power supply circuit that is coupled between the input terminal and the output terminal and converts the input voltage into a predetermined voltage to output the predetermined voltage;

a smoothing capacitor that is coupled to the output terminal; and

a second power supply circuit that outputs a predetermined voltage or current to the output terminal via the smoothing capacitor, based on a feedback signal corresponding to the predetermined output voltage, and

wherein the power supply circuit serves as the first power supply circuit.

20. The power supply circuit as claimed in claim 19 ,

wherein the first power supply circuit includes a control signal generator circuit that generates a control signal for making constant a current flowing through the load or a voltage dividing resistor of a voltage dividing circuit coupled to the output terminal, to output the control signal to the second power supply circuit, based on the feedback signal.

21. The power supply circuit as claimed in claim 20 ,

wherein the control signal generator circuit includes a differential amplifier that outputs, as the control signal, a voltage difference between the voltage of the feedback signal and a predetermined threshold voltage.

22. The power supply circuit as claimed in claim 19

wherein the first power supply circuit includes a power factor correction circuit.

23. The power supply circuit as claimed in claim 19 ,

wherein the first power supply circuit includes a DCDC converter.